Mullerian – 2 or more unpalatable species resemble each other & both model & mimic appears to be protected due to distasteful look eg. Moth mimics a wasp.

Genetic drift (sewall wright effect) – random change in gene freq in small popln by chance & not by natural selection. It is due to small mating. It disturbs the hardy Weinberg Equilibrium. It occurs in isolated islands rather than in a populated population. It results in elimination of original characters.